Author: Dann Corbit
Date: 23:49:15 09/05/02
Go up one level in this thread
On September 06, 2002 at 01:41:52, Robert Hyatt wrote:
>On September 06, 2002 at 00:05:25, Dann Corbit wrote:
>
>>On September 05, 2002 at 23:44:54, Robert Hyatt wrote:
>>[snip]
>>>That is the point. Super-linear speedup is a direct proof of bad move
>>>ordering, as that is the only way to get one. I get a few (I am going to
>>>post a set of positions for Martin in just a few minutes) but those are
>>>offset (more than offset actually) by less than linear speedups in other
>>>positions...
>>
>>Improved move ordering is one way to get more than linear speedup. But I think
>>that there may be others.
>>
>>Consider chasing the pv with one of the CPU's. As long as you have the move
>>ordering perfect, and you are not running down a blind canyon, you might
>>(should) be getting improvement for each forward ply of the pv. Now, as the
>>second (or nth or whatever) CPU chases along the PV and analyzes, it fills the
>>hash table with goodies about the future. Some other searches will see this
>>{far into the future} data and instead of a ce of +0.2 it is a ce of +1.4. This
>>causes all the poor searches to cut off much more easily. Perhaps it can reduce
>>the tree to 1/10 of its former size.
>>
>>So what I am suggesting is that some *other* searching method than a "brute
>>expansion of the a/b search tree by labor division" might shrink the tree. And
>>not just by move ordering but also by improved cutoffs.
>
>
>If that were to work consistently, the sequential algorithm is easy to
>modify. Create two "pseudo-threads". Search one node on one, then one node
>on the other, and go back and forth. The _same_ synergistic effect should be
>found and the same super-linear speedup should occur, _without_ a parallel
>search at all.
>
>That is _always_ the answer to super-linear. IE in the test results I have
>posted, this algorithm would have helped the serial crafty in 2-3 positions.
>Of course, it would kill it in others as searching two nodes in parallel is
>not a good idea for normal alpha/beta..
Then why is it (he asked himself aloud) that pondering does better when you
guess with extrapolation what is going to be played? Why not just continue to
ponder at the current root instead? There must be some benefit to the
extrapolation or there would be no net gain.
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